Per that article:
'Cuck is also set to include several other controversial song including “Cousins” where West admits to having an incestuous relationship with a cousin when they were both children.
On the song, he raps: “Hanging with my cousin, reading dirty magazines / We seen some ni-gas kissin’, we ain’t know what that shit mean / Then we start re-enacting everything that we had seen / That’s when I gave my cousin head, gave my cousin head / Gave my cousin head, I gave my cousin head / I gave my cousin head.”'